package developer.算法.链表.LRU缓存;

import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;

/**
 * 请你设计并实现一个满足  LRU (最近最少使用) 缓存 约束的数据结构。
 * 实现 LRUCache 类：
 * LRUCache(int capacity) 以 正整数 作为容量 capacity 初始化 LRU 缓存
 * int get(int key) 如果关键字 key 存在于缓存中，则返回关键字的值，否则返回 -1 。
 * void put(int key, int value) 如果关键字 key 已经存在，则变更其数据值 value ；
 * 如果不存在，则向缓存中插入该组 key-value。如果插入操作导致关键字数量超过 capacity ，
 * 则应该 逐出 最久未使用的关键字。
 * 函数 get 和 put 必须以 O(1) 的平均时间复杂度运行。
 * <p>
 * <p>
 * <p>
 * 示例：
 * <p>
 * 输入
 * ["LRUCache", "put", "put", "get", "put", "get", "put", "get", "get", "get"]
 * [[2], [1, 1], [2, 2], [1], [3, 3], [2], [4, 4], [1], [3], [4]]
 * 输出
 * [null, null, null, 1, null, -1, null, -1, 3, 4]
 * <p>
 * 解释
 * LRUCache lRUCache = new LRUCache(2);
 * lRUCache.put(1, 1); // 缓存是 {1=1}
 * lRUCache.put(2, 2); // 缓存是 {1=1, 2=2}
 * lRUCache.get(1);    // 返回 1
 * lRUCache.put(3, 3); // 该操作会使得关键字 2 作废，缓存是 {1=1, 3=3}
 * lRUCache.get(2);    // 返回 -1 (未找到)
 * lRUCache.put(4, 4); // 该操作会使得关键字 1 作废，缓存是 {4=4, 3=3}
 * lRUCache.get(1);    // 返回 -1 (未找到)
 * lRUCache.get(3);    // 返回 3
 * lRUCache.get(4);    // 返回 4
 * <p>
 * <p>
 * 提示：
 * <p>
 * 1 <= capacity <= 3000
 * 0 <= key <= 10000
 * 0 <= value <= 105
 * 最多调用 2 * 105 次 get 和 put
 */
public class LruCache {

    public static void main(String[] args) {

        Solution3 lruCache = new Solution3(2);
        lruCache.put(1, 1);
        lruCache.put(2, 2);
        System.out.println(lruCache.get(1) + "get 1 ");//get1
        lruCache.put(3, 3);
        System.out.println(lruCache.get(2) + "get 2 ");//get1
        lruCache.put(4, 4);
        System.out.println(lruCache.get(1) + "get 1 ");//get1
        System.out.println(lruCache.get(3) + "get 3 ");//get1
        System.out.println(lruCache.get(4) + "get 4 ");//get1
    }


    static class Solution3 {
        int capacity;
        Node head, tail;
        Map<Integer, Node> map;
        boolean isInit = false;


        public Solution3(int capacity) {
            this.capacity = capacity;
            map = new HashMap<>(capacity);
        }

        public void put(int key, int value) {
            if (!isInit) {
                Node node = new Node(key, value);
                head = node;
                tail = node;
                isInit = true;
                map.put(key, node);
                return;
            }


            //如果数据存在 则做替换 随后替换到头节点
            if (map.containsKey(key)) {
                map.get(key).value = value;
                Node node = map.get(key);
                moveToHead(node);
                return;
            }

            if (map.keySet().size() == capacity) {
                //移除数据
                map.remove(tail.key);
                tail = tail.pre == null ? head : tail.pre;
            }
            //将新节点插入前面
            Node node = new Node(key, value);
            head.pre = node;
            node.next = head;
            head = node;
            map.put(key, node);
        }

        public int get(int key) {
            //get后应将选中的节点插到头部
            Node node = map.get(key);
            if (node != null) {
                moveToHead(node);
            }
            return node == null ? -1 : node.value;
        }

        private void moveToHead(Node node) {
            if (node == head) {
                return;
            }

            Node next = node.next;
            Node pre = node.pre;

            pre.next = next;
            if (next == null) {
                tail = pre;
            } else {
                next.pre = pre;
            }

            head.pre = node;
            node.next = head;
            head = node;


        }

        static class Node {
            int key;
            int value;
            Node next;
            Node pre;

            public Node(int key, int value) {
                this.key = key;
                this.value = value;
            }
        }

    }


    static class LRUCache extends LinkedHashMap<Integer, Integer> {
        private int capacity;

        public LRUCache(int capacity) {
            super(capacity, 0.75F, true);
            this.capacity = capacity;
        }

        public int get(int key) {
            return super.getOrDefault(key, -1);
        }

        public void put(int key, int value) {
            super.put(key, value);
        }

        @Override
        protected boolean removeEldestEntry(Map.Entry<Integer, Integer> eldest) {
            return size() > capacity;
        }
    }


    static class LRUCacheSelf {
        Integer capacity = null;
        Map<Integer, Integer> map = new LinkedHashMap<>();

        public LRUCacheSelf(int capacity) {
            this.capacity = capacity;
        }

        public int get(int key) {
            Integer i = map.get(key);
            if (i == null) {
                return -1;
            } else {
                map.put(key, i);
                return i;
            }
        }

        public void put(int key, int value) {
            if (map.size() >= capacity) {
                Integer firstKey = map.keySet().stream().findFirst().get();
                map.remove(firstKey);
            }
            map.put(key, value);
        }
    }

/**
 * Your LRUCache object will be instantiated and called as such:
 * LRUCache obj = new LRUCache(capacity);
 * int param_1 = obj.get(key);
 * obj.put(key,value);
 */
}
